Spacecraft, such as satellites, high-altitude inflatables, and military aircraft, are exposed to a wide range of thermal conditions during service. A side facing the sun is heated by direct solar radiation, while a side facing the void of space is cooled by radiation. Thermal control of the spacecraft is therefore important. Various techniques have been developed in an attempt to maintain the interior of the spacecraft at a temperature suitable for occupancy by human beings and sensitive equipment. However, prior art techniques have displayed a number of drawbacks.
One technique for moderating the temperature of a spacecraft utilizes thermal louvers, which consist of a series of mechanically controlled metal slats that can open and close, effectively increasing and decreasing radiative heat loss, in response to the temperature of the satellite. However, thermal louvers can add excessive weight to the spacecraft, require power to operate, and can be prone to failure.
In another technique, the external surface of the spacecraft is covered with a white coating. The coating is designed to absorb very little solar radiation, yet radiate thermal energy in the infrared spectrum, thus biasing the overall temperature of the satellite structure on which it is disposed towards cooler temperatures. However, while this solution can help limit the upper temperature of the satellite under variable orbital lighting conditions, certain coatings can leave the spacecraft susceptible to large temperature fluctuations. Critical onboard components, such as batteries, can be unduly stressed by excessive cooling unless they are heated by onboard power sources.
Accordingly, it is desirable to provide a variable emissivity material that can passively reduce the temperature extremes experienced by aerospace systems. It is also desirable to provide a variable emissivity material that is lightweight and requires no additional power source to control the temperature of a spacecraft. In addition, it is desirable to provide a method for fabricating a variable emissivity material. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.